- Museum number
- 1958,1201.1732
- Description
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Chronometer watch.
Spring detent escapement.
Enamel dial.
Gold pair-cases.
- Production date
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1807 (inner case)
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1809 (outer case)
- $Inscriptions
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- Curator's comments
- Comment from Anthony G. Randall and Richard Good, Catalogue of Watches in the British Museum. Vol. VI (1990)
Made by Thomas Earnshaw, 1807
Chronometer
Signature: On the barrel bridge 'Thos Earnshaw London 3469'. On the back plate 'Invt et Fecit 876'. On the dial 'THOMAS EARNSHAW INVT ET FECIT N° 876'.
Case: Gold pair cases, the inner with Chester hallmark (see Note) for 1807 and the maker's mark T.H.; scratched 876. The outer with the London hallmark for 1809 and the maker's mark W.M., also punched s and scratched 790, the five-knuckle hinge recessed flush with the edge of the case. Outer case diam. 59.4 mm, h. 18.0 mm. Inner case diam. 53.5 mm, h. over the glass 24.3 mm.
Dial and hands: Similar to registration no. 1958,1201.1731, the dial cracked across a diameter from II to VII. Signed 'THOMAS EARNSHAW INV. ET FECIT No 876'. Gold hands.
Movement:
Dial plate diam. 49.7mm; front plate diam. 43.0mm; back plate diam. 42.3 mm; frame h. 7.6 mm.
Frame: Similar to registration no. 1958,1201.1593 but with a hinge on the dial plate and case catch and spring on the front plate under the dial.
Fusee: Keywind fusee with stop-work and maintaining power, the maintaining power ratchet wheel brass. The barrel arbor with an extended square at both ends, the setting-up-work on the front plate under the dial. The barrel relieved at the lower end to miss the great wheel and without a flange at the upper end. All the steel parts well finished and blued.
Going train: The third and fourth wheels gilded, the ends of the pinions, the pinions and the arbors well finished and polished.
Jewelling: The pivots of the escape pinion arbor and balance staff only in pierced jewels with ends tones. The endstone in the balance cock of clear sapphire set in a blued steel ring.
Escapement: Earnshaw detent escapement, the original detent and brass arm have been removed and replaced with a well-made detent with solid foot, screwed to the underside of the back plate. The original banking has been retained. The brass escape wheel is of the usual form (see registration no. 1958,1201.1592), the teeth slightly marked. The edge and radial impulse planes of the impulse roller have been polished, the other surfaces are grained. The discharge roller jewelled.
Balance: Bimetallic two-armed balance with timing screws set in the rims at the ends of the arms. Brass segment compensation weights, screws on the inside to secure them to the rim. The steel parts of the rims blued, their free movement limited by brass pegs set in the compensation weights going into holes in rings at the end of a thin white steel cross-arm. The cross-arm has a central boss sandwiched between the underside of the balance and a brass boss. Diam. of rim 18.6 mm, h. 1.53 mm.
Balance spring: Flat open coiled spiral steel spring of 7½ turns, dull blued and pinned to a gilded brass overhanging stud, screwed to the back plate.
Going-train counts:
Great wheel (fusee) 60 teeth, slightly marked
Centre pinion 12 leaves, wheel 64 teeth, no crossings
Third pinion 8 leaves, wheel 60 teeth, 4 arms
Fourth pinion 8 leaves, wheel 70 teeth, 4 arms
Escape pinion 7 leaves, wheel 15 teeth, 4 arms
Beats per hour: 18,000
Motion work:
Cannon pinion 12 leaves, steel minute pinion 14 leaves
Hour wheel 42 teeth, minute wheel 48 teeth.
Provenance: Ilbert Collection, purchased by Ilbert from Selfridges in 1930.
Note: Thomas Earnshaw's watch 872/3467 also has an inner case with a Chester hallmark.
- Location
- Not on display
- Condition
- Latest: 2 (2017)
- Acquisition date
- 1958
- Acquisition notes
- Following the successful acquisition of the celebrated Ilbert collection of clocks (1958,1006 collection), prints and other related materials made possible by the generous donation of funds by Gilbert Edgar CBE Ilbert's watches were then acquired using funds provided by Gilbert Edgar, public donations and government funds.
- Department
- Britain, Europe and Prehistory
- Registration number
- 1958,1201.1732
- Additional IDs
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Previous owner/ex-collection number: CAI.1732 (Ilbert Collection)
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Previous owner/ex-collection number: H4 (Ilbert Ledger)
